Telephone signaling system



Patented Feb. 16, 1932 UNITED STATES PATENT OFFICE WILLIAM. H. EDWARDS,or GREAT NECK, NEW YORK, AssIGn'on. 'ro AMERICAN TELE- PHONE ANDTELEGRAPH COMPANY, A conronnrion on NEW YORK TELEPHONE sIeNALiNe SYSTEMApplication filed .Tune 27,

a station. vA further object of the invention consists in providing alocking circuit for said lamp and means for causing therelease of saidlampwhen the subscriber removes the receiver from the switchhook toanswer the call. A further object of the invention consists in providingimproved means. for increasing the voltage applied to the lamp to causeit to break down and operate together with means for reducing theoperating voltage below the minimumrequired for main,-

taining the lamp in operated condition and thereby extinguishing thelamp. The arrangements of the invention will accomplish in acomparatively simple manner certain re sults which in the prior artrequire a complicated relay arrangement thus resulting in saving inequipment and maintenance costs. Other Ob]8CtS and features of theinvention i will appear more fully from the detailed de- 3 scriptionthereof hereinafter given.

In the arrangements of the inventionthe drop in' potential caused by theapplied ringing current across a copper-oxide rectifier bridged acrossthe line at the station provides sufiicient'voltage in addition to thatprovided in the local neon lamp circuit to break down the neon lamp. Dueto the characteristics of theselamps they will stay operated on a lowervoltage than that required to break them 4o down. Consequently when thisexternal voltage is removed, the lamp will stay operated until thecircuit is broken by removing the receiver from the switclihook. Theunidirectional characteristic of the copper-oxide rectifier is utilizedto prevent the eXtin-' guishing of thelamp during the half cycle whenthe polarity of the external voltageis opposed tothat of the localbattery for the r lamp. The copper-oxide rectifier may be replaced witha resistance bridged across the 1931. Serial No. 547,336.

line and the lamp may be connected across the resistance. Under suchconditions apulse-of current of one polarity may be applied to the lineto raise the battery voltage sufficiently to break down the lamp andoperate it. By applying to the line a pulse of current of the oppositepolarity, such as to oppose the local battery, the voltage acrossthelamp may be reduced below that required to maintain the discharge of thelamp and the lamp maybe thus extinguished.

The invention may be more fully under stood from the followingdescription together with the accompanying drawings in the Figs. '1, 2,3 and 4: of which the invention is illustrated. Fig. 1 is. a circuitdiagram illustrat ing a preferred form of the invention; Fig. 3 is amodification thereof. Similar reference characters have been used todenote likeparts in both of these figures. Figs. 2 and 4' are curvesshowing the voltage characteristics of the operating currents for'Figs.1 and 3, respectively. i In Fig. 1 is shown a telephone lineLterminating at a subscribers station. The subscribers station comprisesthe usual ringing apparatus comprising'the condenser 1 and the ringer 2bridged acrossthe line. It also coniprises the induction coil 6condenser I 7, switclihook contacts 8 and 9, the transmitter 10 andreceiver 11. An additional switch-- hook contact 14 is'provided forpurposes to be pointed out hereinafter. Connected either across thecondenser 1 or across the line L is a circuit 3 including a condenser iand a recti her 12 which may be of the copper-oxide type. Connectedacross the rectifier. 12' is a circuit including the battery 13,' thevisual signal. lamp 5 which maybe aneon lamp, and the switchhook contact14;. .When ringing current is applied to the line the drop in poten*tial caused thereby across the rectifier 12 provides suilicient voltagean addition to that provided by the battery 13 to break down the lamp A.neon lamp such as lamp 5 has the characteristic that it will stayoperated at a lower voltage than that required to break it down.Consequently when the external voltage caused by the ringing current isremoved the lampzwill be maintained operated by the voltage of battery13 until the circuit is broken by removing the receiver 11 from theswitchhook and opening the contact 14. The copper-oxide rectifier 12 isutilized and is poled as shown to prevent extinguishing lamp during thehalf cycle when the polarity of the external voltage of the ringingcurrent is opposed to that of the local battery 13.

In Fig. 2 are shown curves illustrating the voltage characteristics ofthe operating currents for the lamp 5. The voltage of the battery 13 isindicated at A. This is between the dotted lines X and Y. X indicatesthe breakdown voltage needed to break down the tube 5. Y indicates theminimum voltage needed to maintain the discharge of the tube after itsbreak down. hen alternating ringing current is applied to the line thevoltage drop across the rectifier 12 will be added to the voltage of thebattery 3 and the peak voltage will exceed the breakdown voltage asindicated at the dotted line cl. Upon the removal of the externalvoltage caused by the ringing current the tube will be held oper ated bythe voltage of battery 13 until switchhook contact 14 is opened. At thispoint, designated 6, the voltage will drop below the dotted line Y andthe lamp will be extinguished. When the receiver is again restored tothe switchhook such as at the point 172., the battery voltage again willfall between the dotted lines X and Y. \Vhen ringing current is againapplied to the line the peak voltage at a point indicated by the dottedline f will rise above the breakdown voltage and again cause the lamp tobe operated.

In Fig. 3 is shown a modification of the invention in which means areprovided for extinguishing the lamp from a point such as the centralofiice rather than upon the removal of the receiver from the switchhook.A line L is shown terminating at a central oflice in the jack J andconnected to a subscribers telephone set. This set includes the usualinduction coil 6, condenser 7, switchhook contacts 8 and 9, thetransmitter 10 and receiver 11. Bridged across the line L at thesubscribers station is a condenser 4 and a resistance 18. Connectedacross the resistance 18 is a circuit including the battery 13 and thevisual signal 5, such as a neon lamp. At the central office is provideda plug P adapted to be connected to the jack J. Associated with the plugP are the switches K and K whereby pulses of current of either positiveor negative polarity may be applied to the line L. If it is desired tooperate the lamp 5 the ke K will be operated. This will apply from thebattery B a pulse of negative current to the tip side of the line L andwill charge the condenser l. The voltage drop across the resistance 18will then be added to the voltage drop of the battery 13, and wouldincrease the voltage drop across the lamp 5 sufiiciently to cause it tobreak down. It will remain operated due to the voltage of the battery13. If it is desired to extinguish the lamp the key K at the centraloflice will be operated. This will apply a pulse of positive current tothe tip side of the line and charge the condenser 4 in the reversedirection. The voltage drop across the resistance 18 will now oppose thevoltage drop of the battery 13 and will reduce the voltage drop acrossthe lamp 5 so that it will be below the minimum voltage needed tomaintain the lamp in a discharging condition. This will extinguish thelamp.

In Fig. 4 are shown the curves A and B illustrating the voltagecharacteristics of the operating currents for the arrangements of Fig.3. When a negative pulse of current is applied to the line L the batteryvoltage will be raised at the point indicated by the dotted line '2' sothat the peak voltage will be sufficient to break down the lamp. Thebattery voltage will then hold the lamp in the operated condition. \Vhena positive pulse of current is applied to the line L the Voltage of thebattery 13 will be reduced at a point such as indicated by the dottedline 8 so that the peak voltage will fall below the minimum voltage tomaintain the tube in the discharging condition and will thus extinguishthe tube.

While the invention has been disclosed as embodied in certain specificforms which are deemed desirable, it is understood that it is capable ofembodiment in many and other widely varied forms without departing fromthe spirit of the invention as defined by the appended claims.

What is claimed is:

1. A transmission line terminating at a station, a signaling circuitbridged across said line at said station, a rectifier included in saidsignaling circuit, and a circuit bridged across said rectifier, saidlast mentioned circuit including a source of potential and a coldcathode discharge tube.

2. A telephone line terminating at a subscribers station, a signalingcircuit bridged across said line at said station, a rectifier includedin said signaling circuit, and a circuit bridged across said rectifier,said last mentioned circuit including a cold cathode discharge tube witha source of potential therefor and circuit breaking means controlled bthe telephone apparatus at said subscriber's station.

3. A transmission line terminating at a station, a signaling circuitbridged across said line at said station, a resistance included in saidsignaling circuit, and a circuit bridged across said resistance elementincluding a source of potential and a cold cathode discharge tube.

4. A transmission line to which signaling currents having components ofeither positive or negative polarity may be applied, a station connectedto said line, a signaling circuit including elements of capacity and reasistance bridged across said line at said station, and a circuitincluding a cold cathode discharge tube and a source of potentialbridged directly across said resistance element whereby the potentialdrop across said resistance of said currents may be utilized to changethe potential applied to said tube.

5. A transmission line interconnecting two stations, means at onestation for applying to said line current of positive polarity and meansfor applying to said line current of negative polarity, a signalingcircuit bridged across said line at said other station having includedserially therein elements of capacity and resistance, and a circuitincluding a cold cathode discharge tube and a source of potentialtherefor bridged directly across said resistance element whereby thevoltage drop across said resistance for current of one of saidpolarities applied to said line Will augment the efiect of said sourceof potential so as to operate said discharge tube and the voltage dropacross said resistance for current of the other of said polaritiesapplied to said line will decrease the efiect of said'source ofpotential so as to release said discharge tube.

In testimony whereof, I have signed my as name to this specificationthis 26th day of June 1931.

' WILLIAM H. EDWARDS.

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